1. Field of the Invention
The present invention relates to tetraene derivatives useful as intermediates to carotenoids, such as lycopene and its analogues, important in the fields of pharmaceuticals, feed additives and food additives, and concerns their manufacturing methods.
2. Related Art
Heretofore, as a synthesizing method of lycopene which is a symmetrical C40 compound, there have been known, for example, a method in which two molecules of a C15 compound and one molecule of a C10 compound are coupled, a method in which two molecules of a C10 compound and one molecule of a C20 compound are coupled (see, for example, Pure & Appl. Chem., Vol. 69, 2039 (1997), Helv. Chim. Acta, Vol. 39, 463 (1956), etc.), and a method in which two molecules of a C8 compound and one molecule of a C24 compound are coupled (see, for example, DE 2554924, etc.). It is, however, difficult to say that these methods are completely suitable because they require one to synthesize two types of compounds separately, which are different in their number of carbon atoms and molecular structure. On the other hand, a method in which two molecules of a C20 compound are coupled, which has been reported in Proc. Chem. Soc., 261 (1961), Liebigs Ann. Chem., 1146 (1977), etc., is thought to be a preferable manner of reaction. However, since it requires multiple steps to synthesize the C20 compound, it does not necessarily have much industrial practicality.